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ACRC Technical Report 206PDF


Title:Single Phase, Two-Phase Modeling; X-Ray Visualization for a Microchannel Manifold Distribution System
Author(s):Thompkins, D.M.; Newell, T.A.; Hrnjak, P.S.
Subject(s):pressure drop
microchannel manifolds
Abstract:In Chapter 1, an experimental investigation of single phase fluid distribution through an array of microchannel discharge tubes was conducted. Span-wise pressure profiles were also obtained. The working fluids were air and water. The distribution manifold was oriented horizontally and the microchannels vertically downward. All tests were adiabatic. The discharge tubes are 6-port aluminum microchannel tubes having a hydraulic diameter of 1.54mm and a cross-sectional area of 1.669x10-5 m2. Three spacer plates (12.7mm, 6.35mm, and 3.175mm) were employed to change the cross sectional area of the manifold distribution channel. This changes the area ratio, defined as the ratio of total available discharge area to total inlet manifold channel area. Several models are developed to predict single phase discharge distribution along the length of the manifold. Special case and approximation-type models are found to grossly under-predict distribution; satisfactory agreement was obtained for generalized non-dimensional and physical, integral models which do not make limiting assumptions. In Chapter 2, the same system was used for two-phase flows of air and water. The inlet mass flux ranged from 50 kg m2 × s to 400 kg m2 × s and the quality ranged from 0 to 0.5. The concept of modeling for twophase flows is first explored in detail, and various approaches are explained. An original model is developed from first principles and applied to the current system. Predictions for quantities such as the total discharge mass flow rate, run quality, and exit qualities are obtained. The model has an advantage over previous models in that only inlet quantities and manifold geometry are specified. In Chapter 3, flow visualization and two-phase pressure drop data were taken for 60.9cm test sections of the microchannels. The working two-phase fluids are air-water and R134a vapor-liquid. Mass fluxes of 50 kg m2 ×s to 300 kg m2 × s and vapor flux qualities ranging from 0 to 1 were employed. In total, six different microchannel orientations are analyzed. Flow maps describing the two-phase flow regimes are constructed using probabilistic time functions instead of conventional maps found in literature. Visualization is performed using an Xray diagnostic device capable of peering through aluminum, in contrast to standard idealized transparent test section visualization methods.
Issue Date:2002-12
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-206
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 138
Date Available in IDEALS:2009-06-10

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